Minimizing scratches in a blade coated paper web by roughening the smooth side of the web prior to the blade coating operation



NT R 3,133,855 LAISJE COATED PAPER WEB I TING 3 Sheets-Sheet 1 DE OF THEWEB OPERATION y 1964 R. T. CARPE MINIMIZING SCRATCHES IN A B BYROUGHENING THE SMOOTH PRIOR TO THE BLADE COA Filed July 24, 1961 May 19,1964 R. T. CARPENTER TCHES MINIMIZING SCRA IN A BLADE COATE BYROUGHENING THE D PAPER W SMOOTH SIDE OF THE WEB PRIOR TO THE BLADECOATING OPERATION 3 Sheets-Sheet 2 Filed July 24, 1961 .Il u r n kl M 4I =I I I EL y 1964 R. T. CARPENTER 3,133,855

MINIMIZING SCRATCHES IN A BLADE COATED PAPER WEB BY ROUGHENING THESMOOTH SIDE OF THE WEB V PRIOR TO THE BLADE COATING OPERATION Filed July24, 1961 3 Sheets-Sheet 5 United States Patent MINIMIZING SCRATCHES IN ABLADE COATED PAPER WEB BY ROUGHENING THE SMOOTH SIDE OF THE WEB PRIOR TOTHE BLADE COAT- ING OPERATION Russell T. Carpenter, Neenah, Wis.,assignor to Kimberly- Clark Corporation, Neenah, Wis., a corporation ofDelaware Filed July 24, 1961, Ser. No. 126,047 5 Claims. (Cl. 162-135)This invention relates to the production of coated paper and is morespecifically directed to a method of formation of the paper 'web toparticularly adapt the web to blade coating operations.

It has been recognized that paper produced in web form either on aFourdrinier or cylinder machine is subject to a variation betweenopposite sides of the web termed in the industry two-sidedness. Inessence, this term relates to a web in which the Wire side of the web ismore rough than the upper or felt side. More in detail, in the formationof the web, that side which is produced in contact with a travelingscreen or cylinder and dewatered, and then dried, loses in the course ofthe operation more of the fiber fines and fillers commonly used in thepaper furnish than does the upper or felt side. Thus there is a greaterconcentration of paper fines and fillers in the upper or felt side ofthe web or sheet and this latter side therefore exhibits a greatersmoothness.

The characteristic of two-sidedness tends to carry through the operationeven when the paper web is well coated on both sides with the usualmineral coating. Compensating steps therefore are normally undertaken toeliminate the two-sidedness characteristic. Commonly, such steps haveinvolved providing the relatively rough wire side in such manner that itmore closely approaches the surface characteristics of the smootherupper side.

This present invention is directed to an opposite feature and involvesthe roughening of the upper or felt side and the presentation of the webwith the opposed sides roughened or in roughened condition to a bladecoating device.

In blade coating devices the web is usually provided with an excess ofthe coating material by suitable means such as a roller applicator, apond or the like; the excess of coating material on the web is thenbladed off to effect a smooth coating. The blade commonly employed forsuch purpose is somewhat flexible. In some instances the coated webpassing beneath such blade is subject to receiving fine scratches whichaffect to some extent the quality of the paper for certain printingoperations such as those of letterpress a-nd rotogravure.

Factors which affect the development of these fine scratches appear toinclude the formation of small particle aggregates in the coatingmaterial itself as well as, in some rare instances, foreign particleswhich may be swept from the fluid lines of the apparatus. In addition,in the usual coating machines employing recirculation systems for thecoating material, hardened particles and coated fiber fines may bepassed around through the system.

The flexible blade then tends to retain such particles and to promotethe production of fine scratch marks.

Roughening of the upper or felt side of the web before presentation ofthe web to the blade coating device for coating of the upper or feltside apparently permits small particles, whatever their source, to passthrough the blade. The particles tend to be immersed in fluid coatingmaterial in the irregularities of the web. Accordingly, the particlespassed do not interfere with the uniformity of the surface of the coatedWeb, since they are surrounded by fluid coating material in theirpassage of the blade. In addition, the web itself with respect totwo-sidedness is improved. Additionally, by the roughening of the web,compensating steps such as the provision of somewhat different coatingcompositions for each side of the web may be substantially eliminated.In this connection it is to be noted that the blade coating methoditself is desirable due to the tendency of such method to provide bothsides of the web with comparable printing characteristics.

Roughening of the web in accordance with the invention is achieved byimposing a continuous controlled pattern on the upper or felt side ofthe base web. Treatment while the web is well wetted facilitates therough ening action; heavier basis weight webs which customarily tend toscratch somewhat more readily are adapted well for the practice of thisinvention.

Roughening is effected in the papermaking operation prior to passage ofthe web to the coating device for the upper or felt side; suitably, thedandy roll, a felt mark, or a steel stack may be provided to impose thepattern. Suitably also, both sides of the web may be impressioned to aiduniformly from one side to the other.

Accordingly, a primary object of the present invention is to provide anew and novel blade coating process in which the web on the papermakingmachine is provided with a controlled pattern prior to being passed tothe coating device.

Another and important object of the invention is to provide novelapparatus arrangements for the practice of the invention.

These and other allied objects of the invention will be more fullyunderstood by reference to the following detailed description andaccompanying drawings wherein:

FIG. 1 diagrammatically illustrates a paper-making machine adapted forcarrying out embodiments of the invention.

FIG. 2 is a view in perspective of a dandy roll useful in the practiceof the invention.

FIG. 3 is an enlarged fragmentary view illustrating the wire of thedandy roll cover of FIG. 2.

FIG. 4 is a sectional view taken on line 44 of FIG. 3.

FIG. 5 is a fragmentary view illustrating the application of a felt inthe practice of the invention.

FIG. 6 is an enlarged sectional view taken on line 66 of FIG. 5.

FIG. 7 is a fragmentary and elevational view illustrating an embodimentin which cooperating knurled rolls serve to effect roughening inaccordance with the invention.

FIG. 8 is an enlarged and fragmentary view illustrating moreparticularly the cooperation of the rolls of FIG. 7.

Referring to the drawings and initially particularly to FIG. 1, thefurnish for the formation of the paper web W is flowed from a head box 1through a slice 2 over an apron 3 to a traveling Fourdrinier wire 4.Wire 4 is carried on breast roll 5 and couch roll 6. A number ofsupporting table rolls are designated by the numeral 7 and perform theusual function of supporting the wire and pumping the water from theweb, breaking the surface tension of the water contained in the formingweb and thereby promoting drainage. The usual stretch rolls aredesignated at 8, and the guide roll which serves to maintain the Wirelimited in its lateral oscillation is indicated at 9. As is well known,such Fourdrinier wires oscillate from side to side to provide some crosslay of the fibers in the web. Section boxes are designated at 10 andserve both to support the moving wire and to further aid in withdrawalof water from the web. Couch roll 6 is commonly driven to effect wirerotation.

In the passage of the forming Web over the wire, Water is flushedthrough the wire and fines of mineral material as well as small fibersfrom the furnish are flushed primarily from the wire side S of the webcontacting the wire. This action occurs at both the table rolls and thesuction boxes. The formed web as it passes the suction boxes containsusually in excess of 80% of water. Suitably, the couch roll 6 is also asuction roll and so contributes to the withdrawal of water from thetraveling web. Under such conditions the web leaving the couch roll willstill contain between about 75%- 85% of water but is self-supporting.

As illustrated in FIG. 1, a dandy roll 11 is provided in contact withthe traveling web on the felt side P. At some distance prior to thecouch roll between the dandy roll and the couch roll, and indicated bythe numeral 12, is a line which extends transversely of the web and istermed the dry line. The dry line is indicative of a condition of thepaper during formation; essentially, the dry line is that position onthe forming wire in which the forming web no longer has free watercovering the surface of the web but has water primarily only within theinterstices of the fibers. Customarily, it is desired to withdraw Waterfrom the web uniformly across the width so that the dry line issubstantially at right angles with the web.

From the couch roll the traveling web passes to the press section.Included in a press section may be a suction press area designated 18and its cooperating press felt indicated at 19. A plain press isidentified by the numeral 20 and its cooperating press felt by thenumeral 21. The numerals 22 and 23 indicate cooperating pressure rolls.This press section as thus described is conventional and the watercontent of the web leaving the press section is approximately 6070%.

The drier 25 is comprised of a plurality of drums 26 and the paper web,in its passage, is supported by a bottom drier felt 27 and the top drierfelt 28. Conventionally, the moisture content of the web leaving thedrier is approximately 4-6%, and the web is in substantial equilibriumwith the atmosphere.

As the web leaves the drier and passes in the direction indicated by thearrows, it enters a steel stack 30 composed of a stack of rolls thelower of which is positively driven and the others of which are turnedby friction. The web leaving the breaker stack is at a temperature ofapproximately 130150 F. and is passed, as indicated in the figure,directly to coating apparatus generally designated by the numeral 35.

This coating apparatus includes a retainer trough 36 for a pond ofcoating composition 37 in which applicator 38 rotates in the directionindicated by the arrow. Pressed into contact with the applicator 38 is arubber covered backing roll 39 which travels in an opposite angulardirection to that of the applicator roll and forms with the applicatorroll a nip 40. The web, traveling at the speed of the backing roll,passes through the nip through a dwell distance 41 to a knife blade 42supported in pressed contact in any convenient manner by the Web andbacking roll. As illustrated in FIG. 1, coating material applied at thenip in excess to the felt side is directed to the blade 42 where theexcess coating material is removed and recirculated to the coatingmaterial system (not shown). From the blade 42 the web passes over drumdrier 44, through driers 45 over tensioning roll 46 and around guideroll 47 to the coating device 48 for application of coating material tothe wire side S of the web.

The composition which is supplied to the web is conventional and inactual practice may cover a wide range of solids contents andviscosities. Exemplary of the composition is coating material having thefollowing characteristics and components: 100 parts by weight of coatingclay, 16 parts by weight of pearl starch (enzyme converted), 1% of soap,caustic to adjust the pH to about 7.2, and water suflicient to providethe solids content at about 59%. The specific gravity of such acomposition is approximately l.42 and conventionally has a viscosity ofabout 695 Brookfield (measured at r.p.m. with a #6 spindle at 50 C.). Inthe practice of this invention in the manner now to be described, thesame coating composition may be applied to each side of the web.

In the apparatus arrangement described hereinbefore and which, as thusbroadly set forth, is conventional, several mechanical changes may beemployed to produce the felt or upper side of the web in a roughenedcondition. Preferably, the web is acted on mechanically while it isstill in a somewhat plastic state, although the imposition of thedesired roughening pattern may be effected by impressioning of the driedweb itself.

More specifically, the dandy roll 11 (FIG. 1) may be provided with acover having a configuration such as that illustrated in FIGS. 2-4inclusive. Pressed engagement of the dandy roll with the web on theFourdrinier wire serves to indent, roughen, and render somewhat open theusually smooth upper felt side. The dandy roll preferably for thispurpose is positioned on the wire somewhat forwardly of the dry line sothat it contacts the web while the web is thoroughly wetted. The dandyroll itself, as illustrated in FIGS. 24 inclusive, is provided with awire 50 formed of a series of parallel warp wires 51 and a series ofparallel shute wires 52. As shown, wire 50 has a twill weave in whicheach of the warp wires 51 passes over its shute wires 52 and under athird shute wire to provide relatively high and long warp knuckles 53.The shute wires themselves each have relatively low knuckles beneathwhich the Warp wire passes. The terms warp and shute are here used inthe conventional sense in connection with wire cloth weaving wherein thewarped wires extend longitudinally of the loom and are crimped to agreater extent than the shute wires.

The wire illustrated in FIGS. 3 and 4 may be utilized with either sideforming the outer web contact surface of the dandy roll. Further, otherweaves which provide a rough surface may be employed. In many instancesthe Fourdrinier wire itself will have a rough surface, and the dandyroll surface may correspond to it.

Close correspondence between the sides of the forming Web, of course,minimizes two-sidedness in the Web as well as aiding the subsequentblading operation.

In FIGS. 5 and 6 a felt arrangement 55 adapted to have felt 56 contactthe upper side of the moving web W is illustrated. Felt 56 is marked orprovided with alternate raised and lowered portions 57 and 58respectively. These markings may be in any desired pattern to provide aroughened surface of the web. The felt 56 thus provides an alternativemethod of imposing a surface configuration on the web which, at thepress section, is still relatively plastic and impressionable by themoving felt.

FIGS. 7 and 8 illustrate a pair of cooperating rolls 22a, 23a which havebeen substituted for the smooth roils 22, 23. Roll 22a has a surface 60knurled as indicated at 61 to cooperate with the surface 62 which isalso knurled as indicated at 63. In this instance both web surfaces arealtered to achieve close correspondence between the opposite sides ofthe web.

In a manner similar to that described in connection with FIGS. 5 and 6the top drier felt 28 (FIG. 1) may be marked to impose a controlledpattern on the web as it passes over the drier. Similarly, the lowerstack rolls in stack 30 may be knurled, relieved, formed withprotuberances or recesses, or otherwise provided with a pattern formarking and roughening the web W as it moves through the stack. Ingeneral, the roughening action tends to affect the sheet less when thepattern is imposed while the sheet is plastic.

Thus, in effect, to achieve improved blade coated paper webs it is onlynecessary to provide the felt side roughened prior to passing the Web tothe coating device and then to blade coat the so roughened web. Ingeneral, the procedure of invention, while applicable to all webs, ismore important in connection with heavier basis weight webs. It is inthis area particularly that scratching of the coated sheet may occur.

It will be understood that this invention is susceptible to modificationin order to adapt to diiferent usages and conditions and, accordingly,it is desired to comprehend such modifications within the invention asmay fall within the scope of the appended claims.

What is claimed is:

1. In a process for producing printing paper in which a newly formedtraveling web of paper having a relatively smooth and a relatively roughside is dried, coated, and subjected to a knife blade operation whilesupported on a backing roll to smooth and remove excess coating from theweb, the steps of imposing a configurated pattern on the smooth web sideprior to the coating thereof to roughen the said side, subsequentlyapplying an excess of aqueous mineral coating containing pigment andadhesive to the said side, and thereafter blading the excess of coatingfrom said side and smoothing the remaining coating thereon.

2. In a process for producing printing paper in which a newly formedtraveling web of paper having a relatively smooth and a relatively roughside i dried, coated, and subjected to a knife blade operation Whilesupported on a backing roll to smooth and remove excess coating from theweb, the steps of imposing a configurated pattern on the smooth web sidewhile the web is Wet and somewhat plastic and prior to the coating ofsaid side to roughen the said smooth side, subsequently applying anexcess of aqueous mineral coating containing pigment and adhesive to thesaid side, and thereafter blading the excess of coating from said sideand smoothing the remaining coating thereon.

3. In a process for producing printing paper in which a newly formedtraveling web of paper having a relatively smooth and a relatively roughside is dried, coated, and subjected to a knife blade operation whilesupported on a backing roll to smooth and remove excess coating from theweb, the steps of imposing a configurated pattern on the smooth web sidewhile the web is wet and somewhat plastic and before the forming webreaches the dry line and prior to the coating of said side to roughenthe said smooth side, subsequently applying an excess of aqueous mineralcoating containing pigment and adhesives to the said side, andthereafter blading the excess of coating from said side and smoothingthe remaining coating thereon.

4. In a process for producing printing paper in which a newly formedtraveling web of paper having a relatively smooth and a relatively roughside is dried, coated, and subjected to a knife blade operation whilesupported on a backing roll to smooth and remove excess coating from theweb, the steps of imposing a configurated pattern on the smooth web sidewhile the web is wet and somewhat plastic and prior to the coating ofsaid side to roughen the said smooth side, to the same extent as thementioned rough side subsequently applying an excess of aqueous mineralcoating containing pigment and adhesive to the said side, thereafterblading the excess of coating from said side and smoothing the coatingthereon, and subsequently coating the second and opposite side of thepaper Web with the same coating composition.

5. The process of producing printing paper which comprises:

(a) forming a traveling paper web having a relatively smooth felt sideand a relatively rough wire side;

(b) while the web is formed and wet and plastic imposing a continuouscontrolled pattern on the felt side of the web to roughen and open thefelt side;

(c) drying the web with the felt side in the roughened open condition;

(d) applying to the roughened open and dried 'felt side an excess of anaqueous mineral coating composition containing pigment and adhesive;

(e) carrying the web with the excess of coating composition thereon on arubber covered backing roll to a flexible blade pressed against the webon the backing roll;

(1) removing the excess of aqueous mineral coating composition from thetraveling web with the flexible blade while smoothing the remainder ofthe coating on the web;

'(g) said roughened open condition of the web providing for passage ofsmall particle aggregates in the coating remaining on the web withoutsubstantial scratching of the coating; and

(it) subsequently drying the coated web.

References Cited in the file of this patent UNITED STATES PATENTS1,369,186 Perry Feb. 22, 1921 1,501,493 Koplin July 15, 1924 2,156,046Alt Apr. 25, 1939 2,186,957 Collings et a1. Jan. 16, 1940 2,216,803Benda Oct. 8, 1940 2,287,161 Ball June 23, 1942 OTHER REFERENCES Calkin:Modern Pulp and Papermaking, 3rd edition, Reinhold Publishing Corp.,N.Y., 1957, page 331. (Copy in Scientific Library.)

McGraw-Hill, Manufacture of Pulp and Paper, vol. 5, McGraw-Hill BookCo., N.Y., 1939, section 6, page 31. (Copy in Div. 25.)

2. IN A PROCESS FOR PRODUCING PRINTING PAPER IN WHICH A NEWLY FORMEDTRAVELING WEB OF PAPER HAVING A RELATIVELY SMOOTH AND A RELATIVELY ROUGHSIDE IS DRIED, COATED, AND SUBJECTED TO A KNIFE BLADE OPERATION WHILESUPPORTED ON A BACKING ROLL TO SMOOTH AND REMOVE EXCESS COATING FROM THEWEB, THE STEPS OF IMPOSING A CONFIGURATED PATTERN ON THE SMOOTH WEB SIDEWHILE THE WEB IS WET AND SOMEWHAT PLASTIC AND PRIOR TO THE COATING OFSAID SIDE TO EXCESS OF AQUEOUS MINERAL COATING CONTAINING PIGMENT ANDADHESIVE TO THE SAID SIDE, AND THEREAFTER BLADING THE EXCESS OF COATINGFROM SAID SIDE AND SMOOTHING THE REMAINING COATING THEREON.